Inertial sensors are devices such as gyroscopes and accelerometers that have numerous applications in processing orientation, direction, velocity and/or positional information without using an external reference. Some applications include navigation and identifying orientation/direction in rockets, missiles, aircraft, vessels and vehicles as well as many consumer and commercial products like those in the gaming industry.
As the size and cost of inertial sensors have decreased, they have been widely adopted. As an example of usage, inertial navigation systems, inertial measurement units and inertial guidance systems typically include multiple gyroscopes and accelerometers that enable measurement of heading and orientation well as motion change along multiple axes. Such systems are used, for example, in airplane/vessel navigation, missile guidance and unmanned aerial vehicle stabilization. Some gyroscopes are composed of mechanical components while other gyroscopes can be at least partially implemented electronically, such as by using microelectromechanical systems (MEMS).
One of the limitations in the application of inexpensive gyroscopes is the errors that affect the inertial sensor measurements such as gyroscope bias, accelerometer scale error and vibration rectification coefficients. As an example, there is uncertainty in the bias values for gyroscopes as they cycle from turn-on to turn-on. Such bias affects the accuracy and limits the usefulness of the measured signals and the ensuing applications. One prior solution to bias uncertainty was to place the system into a non-rotational environment to allow the bias to be measured prior to operation of the system. For this initialization process, the system is not rotating and any sensed rotation must be the bias and thus can be removed during processing. For certain applications, such as moving vehicles/vessels and airborne assets, such an initialization environment cannot be easily provided. There is a need, therefore, for a system and method in which the gyroscope bias and other inertial sensor errors can be determined in a dynamic or moving environment. Any such solution opens up the potential to use inexpensive gyroscopes in further applications and with greater accuracy.